Stress development in drying coatings after solidification

Abstract

As a coating solidifies by drying, it tends to shrink. It is liquid enough in early stages

A novel technique for in situ measurements of stress development within a drying film

“…In phase III, a constant stress suggests that the system may reach a frozen state. At this stage, the amount (and the rate) of moisture loss becomes very limited and, as a result of this, there should be very limited stress increase, but the film becomes very rigid and solid enough to support the stress (Lei et al, 2002). The relaxation for such a film approaches infinite long and the stress will remain unless a cracking or physical bending to release the stress.…”

“…This could be partly because that the material at this stage is still flowable and highly flexible for fast stress dissipation and partly because that the moisture content gradient is still small due to fast moisture migration from the interior to the surface. It was believed that, at this stage, the fluid coating is liquid enough that any shrinkage stress is rapidly relieved by viscous flow (Lei et al, 2002). However, the two processes changes its places in the second phase, where the moisture content gradient is well established but the stress relaxation becomes limited.…”

Stress development in drying fibers and spheres

“…A finite element program similar to that used by Lei and coworkers7, 8 was developed to solve for the drying and stress development in axisymmetric fibers and centrally symmetric spheres.…”

Mechanics of drying colloidal dispersions: Fluid/solid transitions, skinning, crystallization, cracking, and peeling

“…The groups of Scriven at Minnesota42, 43 and Lewis at Illinois44 first quantified the tensile stress associated with drying films of a few square centimeters with the classic cantilever technique. Typically, for latices that deform viscously in response to capillary pressure, the stress increases as t 3/2 after the dispersion becomes close packed, reaching a maximum that is proportional to ${{\eta \dot E} \mathord{\left/ {\vphantom {{\eta \dot E} H}} \right.…”